The tiny islands in the East China Sea are called Senkaku in Japanese and Diaoyu in Chinese. / Kyodo News via AP

by Calum MacLeod, USA TODAY

by Calum MacLeod, USA TODAY

BEIJING â?? China established the East China Sea Air Defense Identification Zone on Saturday, and its Defense Ministry said it would take "defensive emergency measures" against unidentified aircraft that enter the zone.

A map and coordinates published Saturday showed the zone covers most of the East China Sea and includes a group of uninhabited islets whose ownership is disputed by China and Japan.

Situated in potentially energy-rich waters, the islands are known as the Senkaku in Japan, and the Diaoyu in China. They remain controlled by Tokyo, but Beijing says they belong to China and has grown more assertive in the past year in staking that claim. Increased numbers of Chinese boats and planes have crossed into Japanese waters and airspace to visit the area.

Saturday morning, the Chinese air force promptly conducted its first patrol of the new air zone.

"The patrol is in line with international common practices, and the normal flight of international flights will not be affected," said Shen Jinke, a spokesman for the People's Liberation Army air force, according to the Xinhua news agency.

The zone itself, similar to those established by more than 20 countries worldwide, is "a necessary measure taken by China in exercising its self-defense right," Chinese Defense Ministry spokesman Yang Yujun said on the ministry's website. "It is not directed against any specific country or target. It does not affect the freedom of over-flight in the related airspace."

Japan and the United States saw China's move differently.

"Setting up such airspace unilaterally escalates the situations surrounding Senkaku islands and has danger of leading to an unexpected situation," a Japanese Foreign Ministry statement said Saturday. The ministry lodged a protest at China's Embassy in Tokyo.

The United States is "deeply concerned" by China's new zone, Secretary of State John Kerry said in a statement Saturday.

"We view this development as a destabilizing attempt to alter the status quo in the region. This unilateral action increases the risk of misunderstanding and miscalculations," Kerry said from Geneva, where he was participating in Iran nuclear talks.

Echoing Kerry's words, Secretary of Defense Chuck Hagel said, "This announcement by the People's Republic of China will not in any way change how the United States conducts military operations in the region. â?¦ We remain steadfast in our commitments to our allies and partners."

The United States maintains a significant military presence in Okinawa, Japan, not far from the islands.

The tussle is one of several maritime and territorial disputes China is pursuing with its many neighbors in northeast and southeast Asia. China also claims a huge swath of the South China Sea, where Vietnam and the Philippines have been the most vocal in objecting to China's increasingly muscular approach.

The tiny islands in question have become sensitive nationalist issues in both China and Japan, increasing popular pressure on both governments.

In China, where Japan's wartime actions are kept alive in TV series, films and government propaganda, the new zone quickly won approval from Chinese nationalists, some of whom flocked to online sites such as the militant Iron and Blood forum to demand "merciless" treatment of the Japanese.

On Sina Weibo, China's Twitter equivalent, lawyer Wu Yu, based in the eastern city of Nanjing, demanded the shooting down of all unauthorized planes in Diaoyu airspace.

The zone "is the best news I have seen in my life, China has finally made a move on the Diaoyu Islands," he wrote. "I hope it can live up to its word and will not disappoint the people once again."

Now that China's air defense zone overlaps Japan's pre-existing zone, some worry an accident could spark conflict, wrote military commentator Wu Ge, also on Sina Weibo.

Wu doubts real conflict will ensue but expects the "atmosphere of battle will strengthen nationalist fanaticism" and allow the government to tighten control of society, reap its own rewards and further deprive the public of its rights, he wrote. "They pretend to be tough to win public support."